import java.util.HashMap;
import java.util.Map;

public class Leetcode {
}
//leetcode:525:连续数组
class Solution1 {
    public int findMaxLength(int[] nums) {
        Map<Integer,Integer> hash = new HashMap<>();
        hash.put(0,-1);
        int sum = 0,ret = 0;
        for(int i = 0 ; i < nums.length; i++){
            sum += nums[i] == 0 ? -1:1;
            if(hash.containsKey(sum)){
                ret  = Math.max(ret,i-hash.get(sum));
            }else{
                hash.put(sum,i);
            }
        }
        return ret;
    }
}
//leetcode:1314:矩阵区域和
class Solution2 {
    public int[][] matrixBlockSum(int[][] mat, int k) {
        int m = mat.length,n = mat[0].length;
        int[][] dp = new int[m+1][n+1];
        for(int i = 1;i <= m;i++){
            for(int j = 1;j <= n;j++){
                dp[i][j] = dp[i-1][j] + dp[i][j-1] - dp[i-1][j-1] + mat[i-1][j-1];
            }
        }
        int[][] ret = new int[m][n];
        for(int i = 0;i < m;i++){
            for(int j = 0; j <n;j++){
                int x1 = Math.max(0,i-k)+1,y1 = Math.max(0,j-k)+1;
                int x2 = Math.min(m-1,i+k)+1,y2 = Math.min(n-1,j+k)+1;
                ret[i][j] = dp[x2][y2] - dp[x1-1][y2] - dp[x2][y1-1] + dp[x1-1][y1-1];
            }
        }
        return ret;
    }
}